1. Field of the Invention
This invention generally relates to reactive hot-melt adhesive and/or sealing compositions containing a particulate filler providing improved toolability, wettability and cure profile times, among other things. The invention also relates to a method of using such a sealing composition to fill a cavity or recess in a substrate or between substrates, and the filled articles formed thereby.
2. Description of the Related Art
Adhesive sealants, caulks, and the like, are generally known which incorporate fillers in order to adjust certain physical characteristics of the material such as viscosity and other rheological features such as slumping, weight, toughness, flexibility, resilience, and so forth. Fillers and reinforcing agents generally are selected to have such chemical and temperature resistance so that they might be unaffected by processing with either reactive or thermoplastic systems.
However, in general, prior adhesive sealants are not thought to be entirely satisfactory. For instance, prior adhesive sealants do not have the capability of being shaped or tooled into intricate shapes and/or, if curable, the sealant material cures too slowly. Examples of such needed intricate shapes are seams observed where doorskins are attached to door frames on some new automobiles or the body side seam on some new models of leisure vans. Further, a fast curing adhesive sealant would be highly desirable, such as in the automotive aftermarket, so that as it can be handled more immediately after application without being too tacky, or leaving fingermarks, and so that it can be overpainted without delay.
Regarding previously proposed sealant formulations in more detail, U.S. Pat. Nos. 4,214,019 and 4,252,712 to Donnermeyer et al. describe a block copolymer hot melt adhesive composition and a method for filling a cavity in a substrate with the adhesive. The adhesive composition contains a block copolymer, aluminum powder, glass fiber and hollow inorganic silicate microspheres. The microspheres are said to be required in a minor amount sufficient cause further increase in the melt viscosity with the amount limited so that flow and workability are not impaired. To meet these objectives, an amount microspheres of generally up to about 10 volume percent of the total composition is stated as being required.
As a slight variant to the above, U.S. Pat. Nos. 4,214,019 and 4,217,376 to Donnermeyer et al. describe a block copolymer hot melt adhesive composition and a method for filling a cavity in a substrate with the adhesive, wherein the adhesive composition contains a block copolymer, particulate inorganic reinforcing agent, glass fiber and hollow inorganic silicate microspheres. Again, an amount microspheres of generally up to about 10 volume percent of the total composition is stated as being required. Also, the Donnermeyer et al. patents all relate to nonreactive adhesive systems.
U.S. Pat. No. 4,388,424 to Kennell et al. describe an ambient or room temperature caulk or sealant composition that is extrudible or trowellable. The caulk or sealant composition contains an acrylic copolymer latex binder, glass microballoons, plasticizer, solvent, water adhesion promoters, mineral filler and/or coloring pigments, and the like. The microballons are said to increase the thermal insulation properties and decrease the shrinkage properties in the dried caulk seam as well as impart good extruding characteristic during application and curing of the caulk at ambient temperatures.
As known, setting or hardening of adhesives, including adhesive sealants, into a solid form occurs in three different basic ways: by cooling, by solvent removal, or by a chemical reaction. Of the three, it is generally understood that solvent-based adhesives, such as described by Kennell et al., typically suffer the greatest shrinkage during solidification (solvent removal). Such shrinkage can greatly undermine the performance of an adhesive sealant since the sealant needs to make and maintain intimate contact with the surfaces of the cavity or recess being filled. Kennell et al. does not relate to adhesive sealants which set by cooling and/or chemical reaction. Also, unlike hot melts, solvent-based sealant systems cannot be formulated as 100% solids, and thus have associated higher costs and ecological drawbacks.
U.S. Pat. No. 4,005,033 to Geogeau et al. discloses a solvent-based pasty mastic adhesive or sealant containing organic hollow microspheres, preferably heat expandable thermoplastic spheres. Thermoplastic microspheres generally soften at too low a temperature to be applicable for hot melt applications. The use of thermosetting plastic microspheres in hot melts would be contraindicated due to the risk of the spheres reactivity in the system.
PCT Application WO 92/09503 to Garvey et al., published Jun. 11, 1992, describes a microwave package contining a quantity of hot melt adhesive, where the hot melt adhesive may be of a type which is activatable without microwave susceptors, i.e., of a water retaining type, or may be of a type including microwave susceptors. The microwave susceptor particles include nonsusceptor particles, such as microbubbles or flakes, which are coated with a microwave susceptor layer including a metal or metal -oxide, -silicide, -boride and -phosphide. A hot melt adhesive is exemplified which is loaded with glass microbubbles coated with tungsten.
European Patent Applicant No. 0 455 400, published 6 Nov. 1991 (Stolobie et al.), and PCT Application WO 92/13017 (Kangas), each disclose an adhesive coating or sealant formulation formed of a blend of isocyanate-terminated polyurethane prepolymers. In the case of Kangas et al, this blend consists essentially of a first isocyanate-terminated polyurethane based on the reaction product of a polyhexamethylene adipate and a polyisocyanate and a second isocyanate-terminated polyurethane based on the reaction product of poly(tetramethylene ether) glycol and a polyisocyanate. Kangas disclose a similar adhesive coating but also requiring a third prepolymer comprising the reaction product of an essentially amorphous hydroxy-functional material and polyisocyanate. Stolobie et al. and Kangas each disclose the optional use of other adjuvants in amounts up to 50% weight of the composition either individually or alone. Examples of such adjuvants are listed as being chain extension agents, fillers, metal oxides, minerals, thermoplastic resins, plasticizers, antioxidants, pigments, U.V. absorbers, and adhesion promoters. As examples of fillers, Stolobie et al. and Kangas each similarly list carbon black and glass, ceramic, metal or plastic bubbles; although no bubbles of any kind are demonstrated in the examples of either reference.
Also, conventional plastic (PVC) plumbing drain pipe and joint fixtures, e.g., ells, tees, and the like, are usually joined and sealed using solvent-based adhesives. The solvent-based adhesives set very rapidly and allow only a short period of time to accurately align of the fixtures before the adhesive sets. Also, the solvent-based adhesives have low viscosity and body which can make it difficult to fully seal the joint.
Also, in the conventional construction industry, there is a need for an adhesive and/or sealant which is flexible yet strong upon cure and has a relatively long open time to permit facile tooling in cracks between adjoining concrete slabs, boards, sheet rock, plywood and the like.
It is not thought that the field heretofore has disclosed the use, nor appreciated the advantages, that can be gained by filling hot melt adhesives and reactive or curing hot melt adhesive systems with hollow objects made of inorganic silicate having a certain thermal conductivity.